Disposable medical electrode with laminate contact member

ABSTRACT

An electrode which provides improved performance while being characterized by a very economical construction to enhance disposability of the electrode after a single use in an electrocardiograph, heartbeat monitoring device or the like is shown to include a silver-plated, brass, snap-fastener component having a disc-like portion and a projecting ball-shaped portion. A disc of laminate material having a very thin layer of silver chloride bonded to a layer of silver-nickel alloy is secured to the disc-like portion of the snap-fastener by means of a weld which is located close to the edge of the laminate disc and to the edge of the snap-fastener disc portion, the layer of silver chloride being disposed to face away from the snap-fastener. The electrode further includes a body of electrically insulating material which has a central opening and which has an annular groove extending around the wall of the body opening, this annularly grooved portion of the insulating body being fitted over and sealed to the edge of the laminate disc and the edge of snap-fastener disc portion so that the projecting ball-shaped portion of the snap-fastener is disposed at one end of the body opening in a convenient location to be releasably connected to electrical contact means such as a mating snap-fastener component and so that the opposite end of the body opening cooperates with a portion of the silver chloride layer of the laminate disc to define a cavity which receives and holds an electrolyte paste between the layer of silver chloride and the skin of a patient. In this electrode construction, the advantages in performance known to result from the use of a silver chloride layer on a body of silver material are inexpensively achieved and additional improvement in performance is provided by use of a nickel-bearing silver alloy to support the silver chloride material. In addition, although the electrode construction is characterized by low cost, the construction avoids all possible contact of the electrolyte paste with junctures of unlike metal materials in the electrode, thereby avoiding the development of spurious electrochemical effects so that the electrode provides an accurate, rapidly stabilized signal in physiological measuring apparatus with minimal introduction of noise in the signal traceable to the electrode construction.

United States Patent [191 Robichaud DISPOSABLE MEDICAL ELECTRODE WITH LAMINATE CONTACT MEMBER Robert M. Robichaud, Attleboro, Mass.

[73] Assignee: Texas Instruments Incorporated,

Dallas, Tex.

[22] Filed: Aug. 30, 1971 [21] Appl. N0.: 176,050

[75] Inventor:

[52] U.S. Cl. 128/2.06 E, 128/417, 128/DIG.-4

[51] Int. Cl A61b 5/04 [58] Field of Search 128/206 E, 2.06 R, l28/2.1 E, 2.1 R, 404, 411, 417, 418, DIG. 4

[56] References Cited UNITED STATES PATENTS 3,572,323 3/1971 Yuan 128/206 E 3,487,827 1/1970 Edmark 128/106 E 3,496,929 2/1970 Dominques 128/106 E 3,380,445 4/l968 Frasier 128/206 E Primary Examiner-William E. Kamm A ttomey Harold Levine: J ames P. McA ndrews et a1.

[ 5 7 ABSTRACT Aug. 14, 1973 secured to the disc-like portion of the snap-fastener by means of a weld which is located close to the edge of the laminate disc and to the edge of the snap-fastener disc portion, the layer of silver chloride being disposed to face away from the snap-fastener. The electrode further includes a body of electrically insulating material which has a central opening and which has an annular groove extending around the wall of the body opening, this annularly grooved portion of the insulating body being fitted over and sealed to the edge of the laminate disc and the edge of snap-fastener disc portion so that the projecting ball-shaped portion of the snap-fastener is disposed at one end of the body opening in a convenient location to be releasably connected to electrical contact means such as a mating snap-fastener component and so that the opposite end of the body opening cooperates with a portion of the silver chloride layer of the laminate disc to define a cavity which receives and holds an electrolyte paste between the layer of silver chloride and the skin of a patient. In this electrode construction, the advantages in performance known to result from the use of a silver chloride layer on a body of silver material are inexpensively achieved and additional improvement in performance is provided by use of a nickel-bearing silver alloy to support the silver chloride material. In addition, although the electrode construction is characterized by low cost, the construction avoids all possible contact of the electrolyte paste with junctures of unlike metal materials in the electrode, thereby avoiding the development of spurious electrochemical effects so that the electrode provides an accurate, rapidly stabilized signal in physiological measuring apparatus with minimal introduction of noise in the signal traceable to the electrode construction.

7 Claims, 5 Drawing Figures Palemin w 3752.151

SHEET 3 BF 3 f/VI/E/VTOR DISPOSABLE MEDICAL ELECTRODE WITII LAMINATE CONTACT MEMBER At the present time, various types of electrodes are used in electrocardiographs, heartbeat monitoring devices and the like to detect variations in the potential which appear on the skin of a patient and which reflect the heartbeat activity of the patient. As these skin po-- tentials are very small on the order of 2 millivolts the potentials must be amplified to a considerable extent in the physiological testing apparatus to provide effective read-outs reflecting the patients heart activity. For these reasons, the electrodes should be characterized by very high performance to minimize noise factors in the signals transmitted to the testing apparatus by the electrodes. On the other hand, it would be desirable if the electrodes, which are mounted on the patients body during use and which tend to deteriorate in various ways during use, could achieve this high performance while still being sufficiently inexpensive to be discarded after use on a single patient. However, as three to eight or more of the electrodes are conventionally used at one time in performance of physiological measurements on each patient, the electrodes require a very economical construction in order to be adapted for disposable use.

It is an object of this invention to provide a novel and improved medical electrode; to provide such an electrode which is characterized by high quality perfor mance and by a very economical construction; to provide such an electrode which is conveniently attached to the body of a patient and conveniently connected to physiological testing apparatus; and to provide such an electrode which is particularly adapted for disposable use in physiological testing apparatus.

Other objects, advantages and details of construction of the novel and improved medical electrode provided by this invention appear in the following detailed description of preferred embodiments of the invention, the detailed description referring to the drawings in which:

FIG. 1 is a perspective view of the novel and improved electrode provided by this invention;

FIG. 2 is a side elevation view, to enlarged scale, of a component of the electrode shown in FIG. 1;

FIG. 3 is a partial bottom view of the electrode component illustrated in FIG. 2;

FIG. 4 is a side elevation view, partly in section but otherwise similar to FIG. 2, illustrating assembly of the electrode component of FIG. 2 in the electrode of this invention; and

FIG. 5 is a section view along a transverse axis of the electrode of this invention.

Referring to the drawings, the novel and improved medical electrode of this invention includes a rigid, electrically conductive member 12 which has an electrode surface portion and which has a portion projecting from the member to be releasably engaged by electrical contact means. For example, the member 12 preferably comprises a snap-fastener component of conventional configuration (see FIG. 2) having a generally round, disc-like portion 14 with a disc surface 16 to serve as the electrode surface portion of the membet, with an oppositely facing disc surface 18, and with a disc rim and having an additional, integral portion 22, preferably ball-shaped, as shown, projecting from the disc surface 18 to be releasably engaged by electrical contact means such as a mating snap-fastener component and lead indicated by the broken lines 24 and 25 in FIG. 1. Preferably, the electrically conductive member 12 is formed of silver-plated brass although other electrically conductive materials such as brass or copper or other silver-plated or nickel-plated metal materials can also be used within the scope of this invention.

In accordance with this invention, an element 26 of laminate material, preferably of round, disc-like configuration having approximately the same diameter as the disc-like portion 14 of the member 12, is preferably disposed on the electrode surface 16 of the electrically conductive member so that the laminate element and the member 12 are in electrically conductive relation to each other and so that the edge 28 of the laminate element is substantially aligned with the disc rim 20 of the member 12. See FIG. 2. (The element 26 is shown slightly spaced from the member 12 in FIG. 2 only for clarity of illustration and is preferably disposed flat against the surface 16 of the member 12.) For example, the element 26 desirably embodies a layer 30 of silver material having a very thin layer 32 of electrochemically active silver chloride material bonded to the layer 30. In this way, the outwardly facing surface of the silver chloride layer 32 serves as the electrode surface portion of the conductive member means formed of the member 12 and the laminate element 26, and the electrode 10 of this invention is adapted to inexpensively provide the known advantages in performance commonly associated with the use of a silver chloride electrode surface supported on a silver material in a medical electrode. Most desirably, however, the layer 30 of the laminate material is formed of an alloy of silver having a hardness in fully annealed condition of at least about diamond pyramid hardness (DPI-I) and having a hardness in substantially fully hard condition in the order of about 120 diamond pyramid hardness (DPH). Most desirably, the alloying constituent or constituents incorporated with silver in the alloy consist of materials which are electrochemically inactive when used in a particular electrolyte such as an aqueous sodium chloride solution or the like. For example, in a preferred embodiment of this invention, the laminate layer 30 is formed of a silver-nickel alloy having a nominal composition, by weight, of 99.7 percent silver and 0.3 percent nickel. When this preferred material is utilized in the layer 30 it is found that the laminate material embodied in the element 26 is readily produced in strip form by inexpensive roll-bonding techniques with a very thin layer 30 having a thickness of about 0.0019 inches and a hardness of about diamond pyramid hardness (DPH) and with a very thin, but substantially continuous layer 32 of silver chloride having a thickness of less than about 0.0002 inches and preferably of about 0.00015 inches. Use of this material in the laminate layer 30 permits economy in electrode manufacture by permitting use of very thin layers of the relatively expensive layer materials in the laminate 26 while achieving all of the advantages known to be obtained with the silver chloride electrode construction. Use of this silver'nickel alloy in the layer 30 also achieves additional electrode performance advantages including improved stability of the electrical properties of the electrode during use and improved uniformity of electrical properties from electrode to electrode. An additional advantage obtained through use of this alloy material in the laminate layer 30 is avoidance of undesirable light-responsive properties such as are found to be present where a fine silver material is used as a support for a layer of silver chloride in other known medical electrodes.

In a preferred embodiment of this invention, the laminate element 26 is secured in good electrically conductive relation to the snap-fastener member 12 by means of a small weld 34, preferably a resistance or pressure weld, which is most desirably located very close to but slightly spaced from the edge 28 of the laminate element and the rim or edge 20 of the snap-fastener disc portion 14. For example, where the element 26 and the snap-fastener disc portion have diameters of about 0.500 inches, the weld 34 preferably has a diameter a of about .032 inches and is spaced at a distance b of about 0.032 inches from the edges of the laminate disc and of the snap-fastener disc portion.

In accordance with this invention, the electrode further includes an electrode body 36 formed of electrically insulating material such as a polyethylene. The electrode body has a central opening 38 extending through the body and, as shown in FIG. 5, preferably has an annular groove 40 extending around the wall of the body opening. In this arrangement, the annularly grooved portion of the electrode body is fitted around the edge 28 of the laminate element 26 and the edge of the snap-fastener disc portion 18 for mounting the laminate element and the member 12 so that the projecting ball-shaped portion 22 of the snap-fastener member is disposed at one end of the body opening 38 to be conveniently engaged by electrical contact means such as are indicated at 24 in FIG. 1. Preferably the body groove 40 substantially encloses the weld 34 in the laminate element as shown in FIG. 5. In this arrangement, the opposite end of the body opening 38 cooperates with a portion of the silver chloride layer 32 of the laminate element to define a cavity 42 (see FIG. 5) which is adapted to receive and hold an electrolyte paste (not shown) between the silver chloride layer and the skin of a patient. Preferably the material of the electrode body 36 is fused at the location of the body groove 40 to seal the electrode body to the edge 28 of the laminate element and to the rim portion 20 of the snap-fastener. In a preferred method of construction for example, the electrode body 36 is provided with a configuration such as is shown in FIG. 4 having a shoulder 46 and neck portion 48. The assembled laminate element 26 and conductive member 12 are then rested on the body shoulder 46 as shown and the electrode body is pressed with a die (indicated at 50 in FIG. 4) heated to about 350F. for heating and deforming the shoulder portion 46 and the neck portion 48 of the thermoplastic body material to fuse and conform the body material to the configuration shown in FIG. 5 wherein the body material is fused and sealed to the edge of the laminate element 26 and the rim 20 of the snap-fastener disc portion. Of course any other convenient assembly method could be used.

In a practical embodiment of the electrode 10, a layer 52 of adhesive material such as a conventional pressure-sensitive adhesive is disposed on and adhered to the electrode body 36 around the rim portion 54 of the body and preferably a layer 56 of paper, fabric or other protective material is lightly adhered to the adhesive layer as shown in FIG. 5.

In using the electrode 10, the electrode cavity 42 is level-filled with an electrolyte paste (not shown) such as one of the conventional pastes which embody an aqueous sodium chloride solution as a constituent of the paste. The protective layer 56 is then peeled from the electrode and, after appropriate preparation of a patients skin in conventional manner, the rim portion 54 of the electrode is adhered to the patients skin by the adhesive layer 52 on the electrode. See FIG. 1. In this way, an appropriate thickness of the electrolyte paste is disposed between the silver chloride layer 32 of the electrode and the patients skin while the projecting ballshaped portion 22 of the electrode is disposed to be conveniently engaged by an electrical contact means. As the electrode is small and compact and does notjnclude wire leads hanging from the electrode, several such electrodes can be attached to the patients skin at desired locations on the patients body while the patient is located away from physiological measuring apparatus. The patient can then be moved to the measuring apparatus where each electrode ball portion is conveniently engaged by electrical contact means at tached to a lead extending from the apparatus as indicated in FIG. 1. The electrode is then adapted to provide an electrical signal to the apparatus to indicate the variations in potential which occur at the patients skin and which reflect the patients heart activity. The electrode of this invention provides a very rapidly stabilized signal to the measuring apparatus and, because of the uniformity of the electrical properties of the electrode (from electrode to electrode), provides the stabilized signal with very low and uniform offset voltage thereby facilitating production of a clear and accurate read-out of the signal by the measuring apparatus. Most important, it will be noted that the electrode does not have any junctures of unlike metal materials which are exposed to be inadvertently contacted by the electrolyte paste or other moisture. Thus the electrode is not subject to the occurrence of undesired electrochemical reactions which sometimes occur using prior art electrodes and which sometimes caused the prior art electrodes to provide spurious signals. Where the weld between the member 12 and element 26 is concealed within the groove in the electrode body, any discoloration of the electrode which might tend to occur at the weld location is avoided or concealed to assure a clean appearance for the electrode. It is also found that where prior art medical electrodes embodying fine silver materials are somewhat light responsive and sometimes provide spurious signals in response to changing light conditions, the electrode of this invention which embodies silver-nickel alloy in the layer 30 appears substantially free of this defect. Most important, the electrode of this invention incorporates a minimal number of small, inexpensive and relatively low cost elements which are easily assembled to provide a very low cost electrode construction for greatly enhancing disposable use of the electrode and for achieving the advantages of reliability, uniformity and cleanliness derived from such disposable use.

It should be understood that although preferred embodiments of the invention have been described in detail by way of illustration, this invention includes all modifications and equivalents of the described embodiments which fall within the scope of the appended claims.

I claim:

1. A disposable electrode for use in physiological testing apparatus comprising a rigid, electrically conductive member having a disc-like portion with a rim and with a pair of oppositely facing disc surfaces and having an integral ball-shaped portion projecting from one of said disc surfaces of said disc-like portion to be releasably engaged by electrical contact means, an element of laminate material having a layer of silver and having a surface layer of silver chloride bonded to said layer of silver disposed on the other of said disc surfaces of said disc-like portion of said electrically conductive member in electrically conductive relation to said electrically conductive member with said layer of silver chloride facing away from said electrically conductive member, said element of laminate material and said electrically conductive member being secured in electrically conductive relation to each other by a weld between limited portions of said element and of said disc-like portion of said electrically conductive member, and an annular electrically insulating member having an inner diameter portion mounting said element and said electrically conductive member, said electrically insulating member having a portion which cooperates with at least a portion of said layer of silver chloride to form a cavity for receiving an electrolyte paste and which defines a cavity rim to be engaged with the body of a patient for enclosing said paste in said cavity to hold said paste between said portion of said layer of silver chloride and said patients body, said annular electrically insulating member having an annular groove in said inner diameter portion thereof receiving said rim of said disc-like portion of said electrically conductive member and receiving the edges of said element of laminate material for mounting said element and electrically conductive member and for exposing said ball-shaped portion of said electrically conductive member to be releasably engaged by said electrical contact means while said cavity rim is engaged with said patients body.

2. A disposable electrode as set forth in claim 1 wherein said weld is located adjacent an edge of said element and adjacent said rim of said disc-like portion of said electrically conductive member, said annular groove in said inner diameter portion of said electrically insulating member enclosing said weld therein.

3. A disposable electrode as set forth in claim 1 wherein said electrically insulating member embodies a fusible material and wherein said inner diameter portion of said member is fused to said rim portions of said disc-like portion of said electrically conductive member and said edge portions of said element of laminate material for sealing said rim and edge in said annular groove in said electrically insulating member.

4. A disposable electrode as set forth in claim 6 wherein said electrically insulating member is formed of thermoplastic material and wherein said electrically insulating member is fused to said disc-like portion of said electrically conductive member and to said layer of silver chloride entirely around the peripheries thereof for sealing said rim of said disc-like portion and said edge of said element of laminate material within said annular groove of said electrically insulating material.

5. A disposable electrode for use in physiological testingapparatus comprising a rigid, electrically conductive member having a disc-like portion with a rim and with a pair of oppositely facing disc surfaces and having an integral ball-shaped portion projecting from one of said disc surfaces of said disc-like portion to be releasably engaged by electrical contact means, an element of laminate material having a surface layer of silver chloride which has a thickness at least as small as 0.0002 inches bonded directly to a layer of silver alloy which has at least about DPl-l hardness and which comprises about 0.3 percent by weight of nickel and the balance silver, said element of laminate material being disposed on the other of said disc surfaces of said disc-like portion of said electrically conductive member with said layer of silver chloride facing away from said electrically conductive member and having a weld located adjacent an edge of said element and adjacent said rim of said disc-like portion of said electrically conductive member securing said element in electrically conductive relation to said electrically conductive member, and an electrically insulating member of thermoplastic material mounting said electrically conductive member, said electrically insulating member having a portion which cooperates with at least a portion of said layer of silver chloride to form a cavity for receiving an electrolyte paste and which defines a cavity rim to be engaged with the body of a patient for enclosing said paste in said cavity to hold said paste between said portion of said layer of silver chloride and said patients body, said electrically insulating member having an annular groove therein receiving portions of said rim of said disc-like portion of said electrically conductive member and edge portions of said element of laminate material for enclosing said weld between said element and said electrically conductive member within said groove and being fused to said disc-like portion of said electrically conductive member and to said layer of silver chloride to seal said rim and said edge of said laminate material within said groove for mounting said electrically conductive member and for disposing said ballshaped portion of said electrically conductive member to be releasably engaged by said electrical contact means while said cavity rim is engaged with said patients body.

6. A disposable electrode as set forth in claim 5 having adhesive material disposed on said portion of said electrically insulating member which defines said cavity rim for adhering said electrode to said patient's body.

7. A disposable electrode for use in physiological testing apparatus comprising a rigid, electrically conductive member having a disc-like portion with a rim and with a pair of oppositely facing disc surfaces and having an integral ball-shaped portion projecting from one of said disc surfaces of said disc-like portion to be releasably engaged by electrical contact means, an element of laminate material having a layer of silver alloy embodying about 0.3 percent by weight nickel and the balance silver and having a surface layer of silver chloride bonded to said layer of silver alloy disposed on the other of said disc surfaces of said disc-like portion of said electrically conductive member in electrically conductive relation to said electrically conductive member with said layer of silver chloride facing away from said electrically conductive member, said element of laminate material and said electrically conductive member being secured in electrically conductive relation to each other by a weld between limited portions of said element and of said disc-like portion of said electrically conductive member, and an annular electrically insuing an annular groove in said inner diameter portion thereof receiving said rim of said disc-like portion of said electrically conductive member and receiving the edges of said element of laminate material for mounting said element and electrically conductive member and for exposing said ball-shaped portion of said electrically conductive member to be releasably engaged by said electrical contact means while said cavity rim is engaged with said patients body. 

2. A disposable electrode as set forth in claim 1 wherein said weld is located adjacent an edge of said element and adjacent said rim of said disc-like portion of said electrically conductive member, said annular groove in said inner diameter portion of said electrically insulating member enclosing said weld therein.
 3. A disposable electrode as set forth in claim 1 wherein said electrically insulating member embodies a fusible material and wherein said inner diameter portion of said member is fused to said rim portions of said disc-like portion of said electrically conductive member and said edge portions of said element of laminate material for sealing said rim and edge in said annular groove in said electrically insulating member.
 4. A disposable electrode as set forth in claim 6 wherein said electrically insulating member is formed of thermoplastic material and wherein said electrically insulating member is fused to said disc-like portion of said electrically conductive member and to said layer of silver chloride entirely around the peripheries thereof for sealing said rim of said disc-like portion and said edge of said element of laminate material within said annular groove of said electrically insulating material.
 5. A disposable electrode for use in physiological testing apparatus comprising a rigid, electrically conductive member having a disc-like portion with a rim and with a pair of oppositely facing disc surfaces and having an integral ball-shaped portion projecting from one of said disc surfaces of said disc-like portion to be releasably engaged by electrical contact means, an element of laminate material having a surface layer of silver chloride which has a thickness at least as small as 0.0002 inches bonded directly to a layer of silver alloy which has at least about 90 DPH hardness and which comprises about 0.3 percent by weight of nickel and the balance silver, said element of laminate material being disposed on the other of said disc surfaces of said disc-like portion of said electrically conductive member with said layer of silver chloride facing away from said electrically conductive member and having a weld located adjacent an edge of said element and adjacent said rim of said disc-like portion of said electrically conductive member securing said element in electrically conductive relation to said electrically conductive member, and an electrically insulating member of thermoplastic material mounting said electrically conductive member, said electrically insulating member having a portion which cooperates with at least a portion of said layer of silver chloride to form a cavity for receiving an electrolyte paste and which defines a cavity rim to be engaged with the body of a patient for enclosing said paste in said cavity to hold said paste between said portion of said layer of silver chloride and said patient''s body, said electrically insulating member having an annular groove therein receiving portions of said rim of said disc-like portion of said electrically conductive member and edge portions of said element of laminate material for enclosing said weld between said element and said electrically conductive member within said groove and being fused to said disc-like portion of said electrically conductive member and to said layer of silver chloride to seal said rim and said edge of said laminate material within said groove for mounting said electrically conductive member and for disposing said ball-shaped portion of said electrically conductive member to be releasably engaged by said electrical contact means while said cavity rim is engaged with said patient''s body.
 6. A disposable electrode as set forth in claim 5 having adhesive material disposed on said portion of said electrically insulating member which defines said cavity rim for adhering said electrode to said patient''s body.
 7. A disposable electrode for use in physiological testing apparatus comprising a rigid, electrically conductive member having a disc-like portion with a rim and with a pair of oppositely facing disc surfaces and having an integral ball-shaped portion projecting from one of said disc surfaces of said disc-like portion to be releasably engaged by electrical contact means, an element of laminate material having a layer of silver alloy embodying about 0.3 percent by weight nickel and the balance silver and having a surface layer of silver chloride bonded to said layer of silver alloy disposed on the other of said disc surfaces of said disc-like portion of said electrically conductive member in electrically conductive relation to said electrically conductive member with said layer of silver chloride facing away from said electrically conductive member, said element of laminate material and said electrically conductive member being secured in electrically conductive relation to each other by a weld between limited portions of said element and of said disc-like portion of said electrically conductive member, and an annular electrically insulating member having an inner diameter portion mounting said element anD said electrically conductive member, said electrically insulating member having a portion which cooperates with at least a portion of said layer of silver chloride to form a cavity for receiving an electrolyte paste and which defines a cavity rim to be engaged with the body of a patient for enclosing said paste in said cavity to hold said paste between said portion of said layer of silver chloride and said patient''s body, said annular electrically insulating member having an annular groove in said inner diameter portion thereof receiving said rim of said disc-like portion of said electrically conductive member and receiving the edges of said element of laminate material for mounting said element and electrically conductive member and for exposing said ball-shaped portion of said electrically conductive member to be releasably engaged by said electrical contact means while said cavity rim is engaged with said patient''s body. 